Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759441AbYAXXmA (ORCPT ); Thu, 24 Jan 2008 18:42:00 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755967AbYAXXlr (ORCPT ); Thu, 24 Jan 2008 18:41:47 -0500 Received: from BISCAYNE-ONE-STATION.MIT.EDU ([18.7.7.80]:49838 "EHLO biscayne-one-station.mit.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755900AbYAXXlo (ORCPT ); Thu, 24 Jan 2008 18:41:44 -0500 Date: Thu, 24 Jan 2008 18:40:37 -0500 From: Theodore Tso To: Adrian Bunk Cc: Bodo Eggert <7eggert@gmx.de>, Alan Cox , Andreas Dilger , Valdis.Kletnieks@vt.edu, David Chinner , Valerie Henson , linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, Andreas Dilger , Ric Wheeler Subject: Re: [RFC] Parallelize IO for e2fsck Message-ID: <20080124234037.GJ15858@mit.edu> Mail-Followup-To: Theodore Tso , Adrian Bunk , Bodo Eggert <7eggert@gmx.de>, Alan Cox , Andreas Dilger , Valdis.Kletnieks@vt.edu, David Chinner , Valerie Henson , linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, Andreas Dilger , Ric Wheeler References: <9Mo9w-7Ws-25@gated-at.bofh.it> <9Mo9w-7Ws-23@gated-at.bofh.it> <9OdWm-7uN-25@gated-at.bofh.it> <9Oi9A-5EJ-3@gated-at.bofh.it> <9OiMg-6IC-1@gated-at.bofh.it> <9OlqL-2xG-3@gated-at.bofh.it> <9Orda-3ub-45@gated-at.bofh.it> <20080124230809.GA29120@does.not.exist> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080124230809.GA29120@does.not.exist> User-Agent: Mutt/1.5.15+20070412 (2007-04-11) X-Spam-Flag: NO X-Spam-Score: 0.00 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1705 Lines: 36 On Fri, Jan 25, 2008 at 01:08:09AM +0200, Adrian Bunk wrote: > In practice, there is a small number of programs that are both the > common memory hogs and should be able to reduce their memory consumption > by 10% or 20% without big problems when requested (e.g. Java VMs, > Firefox and databases come into my mind). I agree, it's only a few processes where this makes sense. But for those that do, it would be useful if they could register with the kernel that would like to know, (just before the system starts ejecting cached data, just before swapping, etc.) and at what frequency. And presumably, if the kernel notices that a process is responding to such requests with memory actually getting released back to the system, that process could get "rewarded" by having the OOM killer less likely to target that particular thread. AIX basically did this with SIGDANGER (the signal is ignored by default), except there wasn't the ability for the process to tell the kernel at what level of memory pressure before it should start getting notified, and there was no way for the kernel to tell how bad the memory pressure actually was. On the other hand, it was a relatively simple design. In practice very few processes would indeed pay attention to SIGDANGER, so I think you're quite right there. > And from a performance point of view letting applications voluntarily > free some memory is better even than starting to swap. Absolutely. - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/